Police are appealing for public help as they seek a man who exposed himself in front of two children at a bus stop in south-west Melbourne.

The unknown offender performed a sexual act on himself in the presence of the children at the bus stop on Dunnings Road and Point Cook Road in Point Cook about 4.50pm on Wednesday, July 2.

The children ran westbound on Dunnings Road away from the bus stop.

Investigators have released images of a man they believe could help with their enquiries.

He is perceived to be Caucasian in appearance, about 20 to 30 years of age, with a dark moustache and beard.

He was pictured wearing blue jeans, a black jacket and a black cap.

Anyone who witnessed the incident or has information that could help police in identifying the man is urged to contact Crime Stoppers.